January 14, 2004
NASA Satellite Surface Wind Data
Improve 2-5 Day Weather forecasts
NASA’s QuikSCAT satellite is
providing meteorologists with accurate data on
surface winds over the global oceans, leading to
improved 2- to 5- day forecasts and weather warnings. The increased
accuracy, already being used in hurricane
forecasts, is bringing economic savings and a
reduction in weather-related loss of life,
especially at sea, according to a recent NASA
study.
Robert Atlas, a research scientist at
NASA’s Goddard Space Flight Center in
Greenbelt, Md., demonstrated the initial
beneficial impact of scatterometer data on
weather prediction. In a recent experiment, he
showed how the combined use of data from two
scatterometers can lead to an even larger
increase in the accuracy of weather analyses and
forecasts, especially at the two to five-day
range. One scatterometer is onboard NASA’s
QuikSCAT satellite and the other is on the Japan
Aerospace Exploration Agency’s Midori-II
(ADEOS-II) satellite. In 2003, the Midori-II
instrument became non-operational, but while both
instruments worked, they showed the capability to
improve forecasting. These findings will be
presented on Jan. 14, at the American
Meteorological Society’s Annual Meeting in
Seattle.
“QuikSCAT has led to marked improvements
in daily marine weather analyses, forecasts and
warnings issued by the National Weather
Service,” said Atlas. He added these
improvements are especially beneficial since
“Ninety percent of world trade moves over
the oceans. Using QuikSCAT data clearly improves
economies and saves the lives by giving the
shipping industry more accurate
warnings.”
The SeaWinds scatterometer is the key
instrument aboard QuikSCAT that provides ocean
surface wind speed and direction measurements
that lead to improved prediction of storms at
sea. SeaWinds can acquire hundreds of times more
observations of surface wind velocity each day
than can ships and buoys, and is the only
remote-sensing system able to provide continuous,
accurate and high-resolution measurements,
regardless of weather conditions. The data is
especially valuable where observations are
otherwise sparse — such as the Southern
Hemisphere and tropics.
SeaWinds operates by transmitting
high-frequency microwave pulses to the ocean
surface and measuring the
“backscattered” or echoed radar pulse
bounced back to the satellite.
Atlas added the satellite “provides
better coverage of the Earth’s surface and
allows forecasters to detect storms earlier than
ever before.” Unlike some other satellites,
QuikSCAT’s SeaWinds instrument can
“see” through the clouds and
scrutinize conditions — including rainfall
and wind at the ocean’s surface.
During the 1999 hurricane season, the National
Hurricane Center used QuikSCAT data to identify
eight hurricanes. In those cases, QuikSCAT
detected circulating winds well before other it
could be seen as cloud swirls by other
satellites. Additionally, a previous case study
of Hurricane Cindy in 2000 found that use of
QuikSCAT data lead to substantial reduction in
projected storm intensity and movement errors.
Forecasters in the western United States also
benefit from QuikSCAT data since most of the
weather over the West Coast is produced by storms
originating over the Pacific Ocean, where there
are relatively few surface observations.
QuikSCAT can aid in determining the location,
direction, structure and strength of severe
marine storms that often slam into the area
during the winter. East coast forecasters also
find QuikSCAT data beneficial in the prediction
of intense winter storms, including
nor’easters, which travel up the Atlantic
seaboard and batter coastal areas with gusty
winds and heavy precipitation.
Despite the gains made with QuikSCAT, Atlas
said “NASA is committed to making further
improvements by designing advanced scatterometers
to be sure all storm systems are detected in a
timely manner.”
NASA’s Earth Science Enterprise is
dedicated to understanding the Earth as an
integrated system and applying Earth System
science to improve prediction of climate,
weather, and natural hazards using the unique
vantage point of space.
For more information and images on this
research, visit:
http://www.gsfc.nasa.gov/topstory/2004/ 0114scatterometer.html
For more information about the SeaWinds
scatterometer on the QuikSCAT satellite
on the Internet, visit:
http://winds.jpl.nasa.gov/index.cfm
For more information about radiosondes:
http://earthobservatory.nasa.gov/Library/ WxForecasting/wx2.html
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Contacts:
Rob Gutro
Goddard Space Flight Center, Greenbelt, Md.
AMS Press Room: 206-219-4730
NASA: 301/286-4044
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SeaWinds Spots Gabrielle
Early
The arrows represent wind speed, color and size
indicate the magnitude (larger arrow=stronger
wind). The average vorticity, or spin, of the
atmosphere is indicated by background color
(blue=strongest rotation). This area of low
pressure is indicative of the formation of a
tropical depression. This depression was spotted
using SeaWinds data 10 hours before the National
Hurricane Center classified it as a tropical
depression at 5 p.m. on Sept. 11, 2001. Gabrielle
later strengthened to Hurricane status at 11 p.m.
Sept. 16, after crossing Florida from the Gulf of
Mexico into the open Atlantic Ocean.
The Right Ingredients
With the right mix of winds and sea surface
temperatures, an ordinary cluster of tropical
thunderstorms can explode into a tropical storm.
These “ingredients” help scientists
forecast movement of these intense phenomena.
Data from Hurricane Erin, September 10-15, 2001.
a) wind speed and direction, QuikSCAT/SeaWinds
b) cloud structure, Visible and Infrared Scanner
(VIRS) on Tropical Rainfall Measuring Mission
(TRMM) satellite, cooperation with NASDA
c) rainfall rates (green, in excess of 2 inches
per hour), Microwave Imager (TMI) and
Precipitation Radar (PR) on TRMM
d) eye warmth (red), Convection And Moisture
EXperiment (CAMEX)
e) Hurricane Erin, GOES, operated by NOAA
North Atlantic Oscillation
East coast forecasters also find QuikSCAT data
beneficial in the prediction of intense winter
storms, including nor’easters, which travel
up the Atlantic seaboard and batter coastal areas
with gusty winds and heavy precipitation. In
January 2003, QuikSCAT and National Weather
Service data showed circling wind anomalies over
the North Atlantic drawing that cold air over the
United States. These anomalies were part of the
North Atlantic Oscillation (NAO), which could be
the major contributor to the US January arctic
blast. The current phase of the NAO tends to
produce more severe winter weather in the north
and eastern U.S. by allowing cold Arctic air to
penetrate more easily from Canada into the US
Eastern US
Forecasters in the western United States also
benefit from QuikSCAT, since most West Coast
weather originates as storms over the Pacific
Ocean, where there are relatively few surface
observations. QuikSCAT/NWS data indicated the
2003 El Niño winds were quite different
from earlier El Niños. Trade winds
weakened over the central equatorial Pacific, and
wind anomalies converged near the middle of the
equatorial Pacific. The converging wind anomalies
kept the warmest sea surface temperature (SST)
anomalies in the middle of the equatorial
Pacific. During the 1997-1998 El Niño,
wind anomalies flowed from west to east across
the ocean, and the warmest SST anomalies reached
South America. Wind anomalies from Aug. 2002 - Jan. 2003.
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